Electrographic liquid developing apparatus



Dec. 17, 1968 G. H. ROBINSON ET AL 3,416,493

ELECTROGRAPHIC LIQUID DEVELOPING APPARATUS Filed July 14, 1965 GENE H- ROBINSON OR VILLE c- RUBEN-BERG INVENTORS XQM/M ATTORNEYS United States Patent 3,416,493 ELECTROGRAPHIC LIQUID DEVELOPING APPARATUS Gene H. Robinson and Orville C. Rodenberg, Rochester, N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed July 14, 1965, Ser. No. 471,860 8 Claims. (Cl. 118-637) ABSTRACT OF THE DISCLOSURE A liquid developing apparatus employing a development plate adapted to support a thin layer of liquid developer on one surface thereof, which apparatus simulates the rolling action used in hand processing of xerographic sheets. A shuttle means comprises a pair of parallel sidewalls in spaced-opposed relationship with the inner facing wall of each sidewall provided with a curved groove for slidingly holding a record member. A liquid manifold, connected through a valve to a supply tank, is mounted on the shuttle means so that it moves with the shuttle means to dispense the proper amount of liquid developer onto the development plate.

The present invention relates to electrography and in particular to an apparatus for developing electrostatic images with liquid developers.

In electrographic recording as typified by xerography and xeroprinting an electrostatic image is formed on an insulating surface which image conforms to the information to be recorded or reproduced. The electrostatic image is developed or made visible by the application thereto of finely divided developer particles which deposit in conformity with the electrostatic image. Known methods of development include cascade development, powder cloud development, magnetic brush development and the so-called liquid development method.

Liquid development has the advantage of greater simplicity, greater speed of operation, improved control and versatility, and with certain developers, of eliminating the fixing step. According to known xerographic liquid developing methods, an insulating record member bearing an electrostatic image is either totally immersed in a tank of liquid developer or is moved over a rotating toning roller which is partially immersed in a tank of liquid developer. The first method has the disadvantage of wetting both sides of the record member and the second method has the disadvantage, due to the high velocity of liquid needed and the great shearing force between the liquid and the image-bearing surface, of causing background and smearing of the image.

It is an object of the present invention to provide a method and apparatus for developing electrostatic images with liquid developers.

It is another object of the invention to provide a liquid developing apparatus employing a development plate adapted to support a thin layer of liquid developer on one surface thereof, which apparatus simulates the rolling action used in hand processing of xerographic sheets.

It is a further object of the invention to provide a liquid developing apparatus which is simple, inexpensive, compact, and which uses a minimum quantity of liquid developer.

According to the preferred embodiment of the present invention an electrostatic image on an insulating surface of a record member is developed by inserting the member into a reciprocatable carriage or shuttle means which is positioned directly above a fiat, stationary, liquid development plate. The shuttle means comprises a pair of parallel sidewalls in spaced-opposed relationship with the inner facing wall of each sidewall provided with a curved groove for slidingly holding the record member. The grooves are parallel and are also in spaced-opposed relation to each other. One end of the member is connected to a corresponding end of the development plate. As the shuttle means is moved across the development plate the record member is rolled into contact with a layer of liquid developer on the development plate. This movement simulates the rolling action used in hand development. The shuttle means is positioned for movement with respect to the development plate in such a way that the discharge opening in the shuttle means (the opening from which the record member leaves the shuttle means) moves in a plane which is adjacent to and parallel to the liquid developer-containing surface of the development plate. By reversing the direction of movement of the shuttle means, the record member is stripped off of the development plate. A liquid manifold, connected through a valve to a supply tank, is mounted on the shuttle means so that it moves with the shuttle means to dispense the proper amount of liquid developer onto the development plate. The movement of the shuttle means back and forth and the opening and closing of the valve can be carried out by hand or can be carried out automatically by employing a DC. reversible motor, a solenoid valve in the liquid developer conduit, and suitable switches actuated by hand or by the movement of the shuttle means.

The present invention will be more fully understood by reference to the following detailed description when read in connection with the accompanying drawing, in which:

The figure is a perspective view of the preferred embodiment of the liquid developing apparatus of the present invention.

Referring now to the figure there is illustrated a carriage or shuttle 2, which comprises two parallel, vertical sidewalls or plates 4 and 6 which are spaced a predetermined distance apart by means of a cross bar 8. Each of the plates 4 and 6 is provided with a circular groove 10 and 12, respectively, for holding an insulating record member (not shown). The shuttle 2 is slidingly supported on a pair of guide rods 14 and 16, each of which is supported on a platform 18 by means of a pair of legs 20 and 22 respectively. A development plate 24 is mounted on a table 26 which is supported on the platform 18 by means of a set of legs 28. The plate 24 and the table 26 are positioned below the shuttle 2 and are spaced between the plates 4 and 6 so that the surface of the plate 24 is tangential to the lower end of the grooves 10 and 12, which together form a discharge opening 15 in the shuttle 2 for the record member. The grooves 10 and 12 form approximately one-fourth the circumference of a circle. An insulating record member having an electrostatic image is slid into the grooves 10 and 12 (with the image-bearing surface facing down) from either end of the grooves 10 and 12. With the record member in position the end of the member adjacent the discharge opening 15 is connected to the development plate 24 by means of, for example, a clamp 30. A suitable drive mechanism, for example, a shaft 32 and a friction drive roller 34 is provided to move the shuttle 2 in the direction shown by the arrow 36. When the shuttle 2 is moved in one direction, the electrostatic image-bearing surface of the record member is rolled or forced into contact with the liquid developer-bearing surface of the development plate 24 simulating the rolling action used in hand development. By reversing the direction of movement of the shuttle 2 the record member is stripped off of the development plate 24.

A manifold 38, which is at least as wide as the image to be devoloped, and which is mounted on the shuttle 2 by means of rods 40 so that it moves with the shuttle 2, is used to dispense a thin layer of liquid developer onto the development plate 24. A liquid developer supply tank 42 feeds liquid developer by gravity through a conduit 44 and through a control valve 46 into the manifold 38. The valve 46 is open only while the shuttle 2 is making its first pass across the development plate 24; it is closed while the shuttle 2 moves back to its original position. The tip of the manifold 38 is spaced approximately 0.5 to 1.0 mm. from the development plate 24 so that the liquid developer forms a meniscus between the manifold 38 and the developer plate 24. Movement of the shuttle 2 with the valve 46 open thus automatically dispenses a uniform layer of liquid developer onto the plate 24. The manifold 38 is mounted so that the liquid developer is dispensed immediately in front of the line of contact between the record member and the development plate 24 as the shuttle 2 moves over the development plate 24.

EXAMPLE 1 A photoconductive recording sheet was positivelycharged and then exposed in a microfilming camera. The sheet, bearing a sixteen times reduced electrostatic latent image, was placed in the shuttle means described above and shown in the figure, by inserting it into the grooves thereof. The sheet was clamped at the lower end and approximately O.2 ml. of developer was dispensed through the manifold so that a meniscus of developer was formed between the manifold and a development plate comprising an etched copper gravure plate. The gravure plate was composed of cells 25 microns deep and 160 microns in diameter with the walls or bridges of the cells being 20 microns thick. Movement of the shuttle means rolled the sheet into contact with the developer, sandwiching the dispensed liquid developer between the sheet and the development plate. The shuttle was then moved in the reverse direction to pick up the processed photoconductive sheet. Processing was accomplished in 2-3 seconds.

EXAMPLE 2 With very little modification, the apparatus described above was adapted to develop organic photoconductors premounted in standard aperture cards. Essentially, the only modification needed was a gravure plate approximately the size of the card aperture. Development was then carried out as in Example 1, with only the photoconductor making contact with the gravure plate.

EXAMPLE 3 The above apparatus was also used in a camera processor which sequentially charged, exposed, and developed a microimage on a photoconductive sheet premounted in an aperture card. The aperture card was transported by rollers past a charging station and an exposure station and then a development station where it was inserted into the grooves in the shuttle means. The card was stopped at the proper position in the shuttle means after which the electrostatic image on the photoconductor was developed by the method of Example 1. After development, the transport mechanism forwarded the card through the shuttle means and out of the processor.

In addition to developing the charged areas of a xerographic sheet, it is possible to carry out reversal development, in which case the uncharged areas are developed, by applying a suitable bias potential between the conducting layer of the xerographic sheet and the development plate. The development plate can have any one of a number of different constructions including a plate having raised and recessed portions such as a sintered metal plate or a typographic plate, or it can be a flat plate having an overlying fine mesh wire screen. The development plate can also be a porous plate. In the case of a porous plate (or a fiat plate having an overlying screen) the liquid developer can be fed thereto from below the surface of the plate. The development plate can be an absorbent pad supplied with liquid developer from a tank directly below the pad with the liquid being in contact with the pad.

The present invention is not limited to the use of the specific construction described above with respect to the preferred embodiment. For example, either or both of the shuttle means (or record member holder) and the development plate can be moved. The only requirement is that there be relative movement so that the discharge opening of the shuttle means moves across the plate. The grooves in the sidewalls of the shuttle means can be curved, straight or any combination thereof. For example, the spaced, parallel sidewalls of the record member holder can be circular plates. The grooves in this case can be in the form of helices which start at the discharge opening at one point on the periphery of the circular sidewall and move toward the center of the circle. In this case, the development plate must also be circular since it must be positioned in a plane which is immediately adjacent to and essentially parallel to the plane through which the discharge opening of the record member holder moves. In this case the development plate can be stationary and the record member holder merely rotated about the axis of the cylinder formed by the two circular sidewalls.

The present invention has been described in detail with reference to the preferred embodiment thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinbefore and as defined in the appended claims.

We claim:

1. Apparatus for developing an electrostatic image on an insulating surface of a record member with a liquid developer comprising:

a development plate adapted to support a layer of liquid developer on one surface thereof, means for slidingly holding said member in spaced overlying relation to said surface of said development plate, said holding means having a discharge opening from which said member is slidingly removed from said holding means during development,

means for connecting the end of said member adjacent said discharge opening to a corresponding end of said plate,

means for relatively moving said holding means and said plate to move said discharge opening of said holding means in one direction across said surface of said development plate in a direction away from said corresponding end of said plate and in a plane adjacent to and parallel to said surface of said development plate whereby the image-bearing surface of said member is rolled into contact with said surface of said development plate, and

means for relatively moving said holding means and said plate in the opposite direction whereby said member is stripped off of said surface of said development plate.

2. The apparatus according to claim 1 in which said holding means comprises a reciprocatable shuttle means comprising a pair of parrallel sidewalls in spaced-opposed position, the inner, facing surface of each of said sidewalls having an elongated groove for receiving an edge of said member, said grooves being parallel and in directly opposed relation to each other, whereby said shuttle means is adapted to slidingly hold said member.

3. The apparatus according to claim 1 including:

means for applying a layer of liquid developer to said surface of said development plate immediately in front of the line of contact between said member and said surface of said development plate during the relative movement of said holding means and said plate in said one direction.

4. The apparatus according to claim 3 in which said holding means comprises a reciprocatable shuttle means comprising a pair of parallel sidewalls in spaced-opposed position, the inner, facing surface of each of said sidewalls having an elongated groove for receiving an edge of said member, said grooves being parallel and in directly opposed relation to each other, whereby said shuttle means is adapted to slidingly hold said member.

5. Apparatus for developing an electrostatic image on an insulating surface of a record member with a liquid developer comprising:

a development plate adapted to support a layer of liquid developer on one surface thereof,

a reciprocatable shuttle means comprising a pair of parallel sidewalls in spaced-opposed relation, the inner, facing surface of each of said sidewalls having a groove for holding one edge of said record member, said grooves being in parallel, directlyopposed relation and defining a discharge opening for removal of said member from said shuttle means,

means for supporting said development plate adjacent to and in spaced, parallel relation to the plane through which said discharge opening moves during the reciprocating movement of said shuttle means, and

means for connecting the end of the record member adjacent said discharge opening to a corresponding end of said development plate.

6. Apparatus for developing an electrostatic image on an insulating surface of a record member with a liquid developer comprising:

a development plate adapted to support a layer of liquid developer on one surface thereof,

a reciprocatable shuttle means comprising a pair of parallel sidewalls in spaced-opposed relation, the inner, facing surface of each of said sidewalls having a groove for holding one edge of said record member, said grooves being in parallel, directly-opposed relation and defining a discharge opening for removal of said member from said shuttle means,

means for supporting said development plate adjacent to and in spaced, parallel relation to the plane through which said discharge opening moves during the reciprocating movement of said shuttle means,

means for connecting the end of the record member adjacent said discharge opening to a corresponding end of said development plate,

means for moving said shuttle means across said development plate in one direction whereby said imagebearing surface of said record member is rolled into contact with said development plate, and

means for moving said shuttle means in the opposite direction whereby said record member is stripped off of said surface of said development plate.

7. The apparatus according to claim 6 including:

means for applying a layer of liquid developer to said surface of said development plate immediately in front of the line of contact between said member and said plate during the movement of said shuttle means across said surface of said development plate in said one direction.

8. A carriage for developing an electrostatic image comprising a pair of parallel sidewalls in spaced-opposed relation, means for connecting said sidewalls to form a unitary assembly, and a pair of parallel, directly-opposed grooves, one in each of the inside, facing surfaces of said sidewalls, said grooves forming at one end thereof, a discharge opening for the removal from said carraige of a flexible record member held between said sidewalls by means of said grooves, and including a liquid developer manifold mounted between said sidewalls and having an elongated liquid dispensing face, said face being parallel to a line drawn between the opposed ends of said grooves at said discharge opening.

References Cited UNITED STATES PATENTS 2,684,901 7/1954 Sabel et al 11717.5 XR 2,774,290 12/ 1956 Mormann 89 XR 2,847,305 8/1958 Walkup 11717.5 XR 2,995,085 8/1961 Walkup 961.4 XR 3,319,604 5/ 1967 Murray et al 118-637 PETER FELDMAN, Primary Examiner.

US. Cl. X.R. 

